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doi:10.2204/iodp.proc.342.201.2017

Methods and materials

The procedure for the description of smear slides is outlined in the “Methods” chapter (Norris et al., 2014a). The following categories are used to quantify the abundance of diatoms and radiolarians in Holes U1403A–U1410A (Table T1):

• 0 = absent (0%).
• P = present (<1%).
• F = few (1%–10%).
• C = common (>10%–25%).
• A = abundant (>25%–50%).
• VA = very abundant (>50%).

Shipboard processing of radiolarian samples is also outlined in the “Methods” chapter (Norris et al., 2014a). Shore-based processing followed a similar method, except that acid digestion preceded cleaning with H₂O₂ and Calgon. Samples were oven dried at 40˚C, weighed, and leached in 10% hydrochloric acid until the reaction ceased. The spent acid solution was decanted, and the sample was then cleaned by heating on a hot plate in a solution of 10% H₂O₂ and Calgon. After effervescence subsided, the sample was washed through a 63 µm sieve. If the residue was not fully clean, the drying, acid leaching, and cleaning steps were repeated. Residues were oven dried at 40˚C and strewn onto one or more microscope coverslips coated in gum tragacanth. The surface of the coverslip was moistened by a gentle breath, and the loose residue was tapped off. The coverslip was inverted and gently placed on a slide bearing 8–10 drops of Canada balsam. Radiolarian abundance, preservation, and zonal assignment are listed for Holes U1403A–U1410A in Table T2.

Semiquantitative abundance estimates of the radiolarian assemblage are derived from the number of radiolarians in a 5 cm³ sample:

• A = abundant (>10,000).
• C = common (2,000–10,000).
• F = few (100–1,999).
• R = rare (<100).
• B = barren.

Preservation of the radiolarian assemblage is recorded as

• G = good (most specimens complete, fine structures preserved).
• M = moderate (minor dissolution and/or breakage).
• P = poor (common dissolution, recrystallization, and/or breakage).

The radiolarian biostratigraphy has been reviewed for all samples assigned to radiolarian zones in Table T2. This review was used to refine correlations with radiolarian zones in the stratigraphic summaries (Figs. F2, F3, F4, F5, F6, F7, F8, F9) and age-depth plots (Fig. F10). Radiolarian biostratigraphy is based on the low-latitude zonation outlined by Sanfilippo and Nigrini (1998) and revised by Kamikuri et al. (2012). Age estimates for radiolarian datums have been recalibrated to the GTS2012 timescale (Gradstein et al., 2012).

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